Google Chrome on a Mac will soon have a handy option added to browser's choice called "confirm to quit." Upon activating the confirmation, Chrome will display a prompt if you press Command+Q -- which you'll then need to hold for another second and a half to actually quit. It's handy for those times when you meant to tap Command+W to close only your current window, but missed. If you quit via the menu bar, the prompt willn't appear.
Revision 64920 marks the feature's arrival in the Chromium for Mac builds, and users who want to give it a go can enable confirm to quit on the about:flags page.